Xerographic developing apparatus



June 22, 1965 R. A. HUNT XEROGRAPHIC DEVELOPING APPARATUS Original FiledNov. 28, 1958 I 2 Sheets-Sheet l FIG. 1

INVENTOR. ROBERT A. HUNT ATTORNEY R. A. HUNT XEROGRAPHIC DEVELOPINGAPPARATUS Criginal Filed Nov. 28, 1958 June 22, 1965 2 Shets-Sheet 2 OWNINVENTOR. ROBERT A. HUNT ATTORNEY United States Patent 3,190,264XERtBGRAPHiC DEVELQPHNG APPARATUS Robert A. Hunt, Wiihrahnm, Mass,assignor to Xerox gor poration, Rochester, N. a corporation of New@riginai application Nov. 28, 1953, Ser. No. 776,348. Divided and thisapplication Dec. 14, 1961, ar. No. 159,26d

ll Claim. (Cl. 118-637) This invention relates to improvements inautomatic xer-ographic reproduction systems and, particularly, toi1nprovements in systems of this type to facilitate the making ofreproductions from microfilm. More specifially, this invention relatesto a xer-ographic developing system and is a division of applicationSerial No. 776,848,

filed November '28, 195 8, in the name of Robert A. Hunt,

now abandoned.

in the process of xerography, for example, as disclosed in CarlsonPatent 2,297,691, issued October 6, 1942, a xerographic plate comprisinga layer of photoconductive insulating material on a conductive backingis given a uniform electric charge over its surface and is then exposedto the subject matter to be reproduced, usually by conventionalprojection techniques. This exposure discharges the plate areas inaccordance with the light intensity that reaches them, and therebycreates an electrostatic latent image on or in the photoconductivelayer. Development of the latent image is effected with anelectrostatically charged, finely divided material, such as anelectroscopic powder, which is brought into surface contact with thephotoconductive layer and is held the-reon electrostaticaliy in axerographic powder image pattern corresponding to the electrostaticlatent image. Thereafter, the developed xcrographic powder image isusually transferred to a support surface to which it may be fixed by anysuitable means.

Since the disclosure in Carlson, many improvements have been made inxerographic devices and techniques, within the scope of the basicCarlson invention. As a result, both manual and automatic machines forcarrying out xerognaphic reproduction processes are in wide commercialuse. The present invention constitutes a further improvement inautomatic xerographic processing systems whereby such systems may morereadily be ernplayed in integrated data processing systems, particularlythose known as unitized data processing systems.

The principal object of the invention is to improve xcrographicdeveloping systems to effect more uniform and consistent development ofelectrostatic latent images on a xerographic plate.

This and other objects of the invention are attained by means of animproved cascade developing system to form a xerographic powder image ofthe latent image produced on a xerogr aphic drum.

A preferred form of the invention is shown in the accompanying drawingsin which:

l is a perspective view of an automatic xerographic processing systemembodying the invention; and

1 16. 2 is a schematic sectional view of the apparatus of the invention.

In the particular embodiment shown in the drawings, the invention isincorporated in a xerographic machine that is a fully automatic,continuous printer for reproducing information contained on microfilmcards. This equipment reproduces copy on a continuous roll of paper,that may have a web width up to 24", from either positive or negativefilm, in either of two magnification ratios: x or X; whereby microfilmimages of different sizes may conveniently be enlarged to the full withof the web. Referring to FIG. 1, the system may be considered to includefour distinct sections for housing 3,190,264 Patented June 22, 1965 theseveral elements thereof, namely, a base section 1, for housing thexerographic drum, the web tensioning and feeding apparatus, as well asthe devices for effecting the xerographic functions of plate charging,image transfer, brush cleaning, etc; an upper section 2, for housing thecard handling apparatus as well as the bulk of the optical system; anend section 3, secured to the left end of the base section, for housingthe xerographic developing apparatus; and a control section 4, mountedon the base section and forward of the upper section, for housingcertain of the electrical equipment required in the system and toprovide a control panel whereon the operator may set selected ones of aplurality of switches for selecting the desired type of operation.

Base section 1 includes tWo side frames that are connected across theirtops by a plate 5, whereby the entire system is supported. Suitablecover plates are included to enclose the mechanism and access doors areprovided on the front of the machine to facilitate repair andadjustment. Upper section 2 includes suitable cover plates for enclosingthe bulk of the card handling apparatus and the optical system, as wellas a card magazine 7 for holding microfilm cards from whichreproductions are to be made, and a receiving magazine 8 to which cardsare ejected after the microfilm image thereon is reproduced. Alsoincluded, is a lever 9 whereby the optical system may be set selectivelyfor 15 or 20X magnification ratio. In addition, a handwheel is providedwhereby the position of the card magazine may be altered relative to theoptical system, in accordance with the longitudinal dimension of theimage on the microfilm card. End section 3 is enclosed by a dusttighthousing and is pivotally mounted on the base section by suitable hinges11, whereby the entire end section of the machine may be swung outwardlyto permit access to the several elements of the developing system, andto permit convenient access to the surface of the xerographic drum forthe purpose of cleaning. The entire structure is specifically arrangedto form a light-tight enclosure in the areas of the optical projectionsystem and the xerographic developing system.

GENERAL DESCRIPTION OF SYSTEM (FIG. 2)

Ifor a general understanding of the xerographic processlng system inwhich the invention is incorporated, reference is had to FIG. 2 in whichthe various system components are schematically illustrated. As in allxerographic systems based on the concept disclosed in the above-citedCarlson patent, a light image of copy to be reproduced is projected ontothe sensitized surface of a xerographic plate to form an electrostaticlatent image thereon. Thereafter, the latent image is developed with anoppositely charged developing material to form a xerographic powderimage, corresponding to the latent image, on the plate surface. Thepowder image is then electrostatically transferred to a support surfaceto which it may be fused by any suitable form of fusing device, wherebythe powder image is caused permanently to adhere to the support surface.

In the system disclosed herein, microfilm cards are placed in a cardmagazine 7 from which they are fed seriatim to a card carriage of a cardhandling apparatus, generally designated by reference character 15,arranged to the rear of the card magazine assembly. Suitable drivingmeans are provided for the car-d carriage whereby it is caused to movethe card past the optical axis of a projection lens system 16 that isilluminated by a projection lamp LMP-3 for the purpose of scanning themicrofilm The microfilm card image is projected downwardly through anadjustable objective lens assembly 17 and then reflected upwardly by anadjustable mirr-or element 2h to either of two transverse mirrorassemblies 21 or 22, in order to vary the length of the optical path,depending on the magnification ratio employed. From mirror assemblies 21or 22., the light image is projected downwardly through a variable slitaperture assembly 23 and onto the surface of a Xerographic plate in theform of a drum 24.

Xerographic drum 24 includes a cylindrical member mounted in suitablebearings in the frame of the machine and is driven in a counterclockwisedirection by a motor M-Z at a constant rate that is proportional to thescan rate of the microfilm card, whereby the peripheral rate of the drumsurface is identical to the rate of movement of the reflected lightimage. The drum surface comprises a layer of photoconductive material ona conductive baching that is sensitized prior to exposure by means of ascreened corona generating device 25, which may be of the type disclosedin Walkup Patent 2,777,957, that is energized from a suitable highpotential source.

The exposure of the drum to the light image discharges thephotoconductive layer in the areas struck by light, whereby thereremains on the drum a latent electrostatic image in image configurationcorresponding to the light image projected from the microfilm card. Asthe drum surface continues its movement, the electrostatic latent imagepasses through a developing station 26 in which a two-componentdeveloping material, which may be of the type disclosed in Walkup Patent2,638,416, is cascaded over the drum surface.

After developing, the xerographic powder image passes a dischargestation 27 at which the drum surface is illuminated by a lamp LMP2,whereby residual charges on the non-image areas of the drum surface arecompletely discharged. Thereafter, the powder image passes through. animage transfer station 28 at which the powder image is electrostaticallytransferred to a support surface web 29 by means of a second coronagenerating device 36 similar to corona charging device 25, mentionedabove.

The support surface to which the powder image is transferred may be ofany convenient type and is obtained from a supply roll 31 and is fedover suitable guide and tensioning rolls and directed into surfacecontact with the drum in the immediate vicinity of transfer coronagenerating device 36. After transfer, the support surface is separatedfrom the drum surface and guided through a suitable heat fusingapparatus 32, whereby the powder image is permanently afiixed to thesupport surface. Thereafter, the support surface is fed over a furthersystem of guide and tensioning rolls and onto a take-up roll 33 that isdriven by motor M3.

After transfer, the Xerographic drum surface passes through a cleaningstation 34 at which its surface is brushed by a cleaning brush assembly35, rotated by a motor M-4, whereby any residual developing materialremaining on the drum is removed. Thereafter, the drum surface passesthrough a second discharge station 36 at which it is illuminated by afluorescent lamp LMP-l, whereby the drum surface in this region iscompletely flooded with light to remove any electrostatic charge thatmay remain thereon. Suitable light traps are provided in the system toprevent any light rays from reaching the drum surface, other than theprojected microfilm image, during the period of drum travel immediatelyprior to sensitization by corona generating device 25 until after thedrum surface is completely passed through the developing station 26.

DEVELOPING SYSTEM (FIG. 2

In order to effect development of the electrostatic latent image formedon the Xerographic drum, the invention includes an improved developingsystem that is particularly adapted to effect uniform and consistentdevelopment,

regardless of drum width, and is specially suited to effect developmenton the 24" wide drum employed on the Xerographic reproduction apparatusdisclosed herein. in addition, the developing system is structurallyarranged to facilitate maintenance thereof and to permit ready access tothe xerographic drum for periodic cleaning.

As mentioned above, the entire developing system is contained in endsection 3 of the apparatus that is formed of a plurality of sheet metalplates that are integrally connected to provide a completely dust-tighthousing and are arranged to be mounted on hinges fixed on base section 1so that the entire developing system may be swung outwardly from themachine to afford access thereto and to the Xerographic drum.

In prior Xerographic processing devices, it was customary to provide adeveloping system having a vertical conveyor apparatus to transportdeveloping material from a collecting point to a system of chuteswhereby the material could be directed into contact with the Xerographicdrum. in such devices the vertical conveyor usually included relativelynarrow conveyor buckets which necessitated lifting the developingmaterial to a substantial height and then distributing it through anelaborate chute system in order to effect proper developing materialdistribution on the drum surface. in the present invention the verticalconveyor system includes relatively wide buckets that are arrangedparallel to the Xerographic drum axis and have a transverse lengthapproximately equal to three-quarters of the width of the drum surface.

in the specific arrangement wn, conveyor system includes a plurality oftransverse buckets 2.46 that are horizontally supported between twoendless belts 247 on opposite sides of the developer system housing andextend over pulleys 248 and 249 that are fixed respectively ontransverse shafts 25% and 251. For actuating the conveyor system, uppershaft 25% is driven through a belt 252 by a motor M-5 that rotatesconstantly while the machine is in operation.

The developing material conveyed upwardly by the conveyor system isdischarged onto an inclined plate 253 that extends transversely acrossthe entire developing system structure, and extends downwardly to apoint at which it forms a transverse slit orifice in conjunction with asheet metal plate 254 of the developer system housing. The slotforrnedby plates 253 and 254 is of sufficient width to pert. i; an adequateflow of developing material into contact with the Xerographic drumsurface, but is suiiiciently narrow to impede the progress of thedeveloping material and cause it to back up on plate 253 to form asubstantial reserve of developing material while the machine is inoperation. Thus, since rate of developer flow is a function of slotwidth rather than head of material, a uniform flow of developingmaterial is maintained at all times. For convenience of maintenance, anaccess door 255 is hinged in an aperture in plate and, together withplate 253, forms a substantia ly continuous surface for transportingdeveloping material.

To minimize undesired bouncing of the developing material within thesystem, a curved baffle plate 256 is 60 secured along the lower edge ofplate 253 and extends transversely across the machine in spaced relationto the Xerographic drum. The spacing is such as to permit completefreedom of movement of the developing material between the plate and theXerographic drum, and the outward curve of plate is effective to guidesubstantially all of the developing material downwardly onto an inclinedtransverse plate 257, whereby the developing material is guided into acollecting bin 25% formed by the cover plates of the apparatus whereinit may conveniently 70 be scooped by conveyor buckets 246.

In order to limit the amount of developing material in collecting bin258, the apparatus includes a catch baffle plate 259 that extendstransversely across the entire developing system housing and has itslower edge spaced 5 from the surface of plate 257 to control the flow ofdeveloping material into the collecting bin. By this arrangement theamount of developing material in bin 258 cannot exceed the height of thelower edge of battle 259. Developing material in excess of this levelbacks up on the incline of plate 257 and is contained by the verticalface of baffle plate 259 to replace the developing material removed frombin 258 by buckets 246. In etfect, plates 257, 259 and the adjoiningside plates for the developer system form a discharge bin for thedeveloping material as it is continuously cascaded over the drumsurface. By this means it is possible to keep a substantially constantsupply of developing material in the collecting bin and to maintain asubstantially constant load on the conveyor system.

In order to replenish the developing material with toner particles asthese are expended in the formation of xerographic powder images, theapparatus includes a toner dispensing mechanism 260 that is disclosed indetail and claimed in my copending application Serial No. 776,976, filedNovember 28, 1958, now Patent No. 3,013,703. Toner dispenser 260 issupported on a suitable bracket 261 in the developing system housing,and is driven from shaft 250 via belt 262, pulley assembly 263 and belt264.

In operation, the toner dispenser functions to sift toner material ontothe developing material that has cascaded over the xerographic drumsurface. In order to ensure uniform distribution of new toner, the tonerdispenser extends horizontally substantially across the drum surface andfunctions to distribute a uniform flow of toner particles throughout itsentire width, in accordance with the dispensing rate required.

To ensure adequate mixing of the toner particles with the developingmaterial, at least a portion of them are caused to deposit on curvedbafile plate 256. To cause these particles to be mixed with theremaining developing material, a narrow slot 255a is formed in accessdoor 255 on guide plate 253 whereby a portion of the material supportedby plate 253 is caused to pass through the slot and over the surface ofplate 256 thereby flushing the toner particles into the developingmaterial supply at the bottom of the housing.

What is claimed is:

In an xerographic developing system for cascading developing materialonto the surface of a xerographic plate, the combination of a collectingbin for containing developing material,

a conveyor for elevating developing material from the collecting bin,

an inclined chute arranged to receive the material from the conveyor andto transport the material to the surface of the xerographic plate,

said chute having a slot formed thereon through which portions of thematerial fall,

a discharge bin arranged below the xerographic plate for receiving thematerial as it is cascaded over the xerographic plate,

said collecting bin and said discharge bin being arranged to eflfectgravity feed of the developing material from the discharge bin to thecollecting bin,

said discharge bin including a baflle means positioned between the sameand the collecting bin for limiting the quantity of developing materialfed from the discharge bin to the collecting bin,

a xerographic toner dispenser positioned above said collecting bin andin discharging relationship thereto for dispensing toner therein, and

a deflecting plate arranged between said chute and said collecting binand below the slot formed therein for receiving said portions ofdeveloping material as they fall through said slot, said deflectingplate extending into the path of dispensing toner and being adapted todirect said portions into contact with the toner being dispensed intosaid collecting bin whereby the dispensed toner becomes mixed with someof the material.

References Cited by the Examiner UNITED STATES PATENTS 1,696,171 12/28Lipsius 118--312 XR 2,173,032 9/39 Wintermute 118-312 XR 2,395,903 3/46Nordquist 118-249 XR 2,633,780 4/53 Watson 118-349 XR 2,810,364 10/57McArthur et al. 118301 2,990,278 6/61 Carlson 117--17.5 XR 3,011,47412/61 Ulrich 11717.5 XR 3,013,342 12/61 Huber et al. 118-637 XR3,043,685 7/62 Rosenthal 117-17.5 XR 3,045,587 7/62 Schwertz 117-175 XR3,053,962 9/62 Cerasani et al 117--17.5 XR

WILLIAM D. MARTIN, Primary Examiner. RICHARD D. NEVIUS, Examiner,

